special petrophysical tools: nmr and image logs core...
TRANSCRIPT
Image Logs
SPECIAL PETROPHYSICAL TOOLS: NMR AND IMAGE
LOGS CORE
LEARNING OBJECTIVES
By the end of this lesson, you will be able to:
Identify the types of image logs and technology used
Identify the application of image logs for geological andpetrophysical data
Integrate the image data with core and other log data toreconstruct depositional models
═════════════════════════════════════════════════════════════════════════
Special Petrophysical Tools: NMR and Image Logs Core
© PetroSkills, LLC., 2016. All rights reserved._____________________________________________________________________________________________
1
COPYRIGHT
FORMATION IMAGING TOOLS – APPLICATIONS
Structural dip
Paleocurrent direction
Thin bed analysis
Textural information (graded beds, bioturbation)
Fracture detection, analysis
Fault identification, characterization
Directional surveys, operational monitoring
In-situ stress estimation (breakout)
BOREHOLE IMAGES
Borehole images are electronic pictures of the rocks and fluids encountered in a wellbore.
Types are electrical, acoustic or video devices.
Images are oriented; they have vertical and lateral resolution.
Case studies show they are best used in conjunction with other wellbore data (logs, cuttings ,cores and production data).
Image Logs ═════════════════════════════════════════════════════════════════════════
2_____________________________________________________________________________________________
© PetroSkills, LLC., 2016. All rights reserved.
COPYRIGHT
ELECTRICAL BOREHOLE IMAGES
Based on dipmeter technology. The tools have microresitivity electrodes arranged around the wellbore that are pressed against the wall.
Trend from a few electrodes to an array of multiple pads.
Data acquisition: tools run in with pads closed; then 4,6 or 8 pads are pressed against the borehole wall.
Electrical current is forced into the rock and sensors measure the current interacting with the formation.
DIPMETERS
═════════════════════════════════════════════════════════════════════════
Special Petrophysical Tools: NMR and Image Logs Core
© PetroSkills, LLC., 2016. All rights reserved._____________________________________________________________________________________________
3
COPYRIGHT
FORMATION IMAGING TOOL MNEMONICS
SLB=Schlumberger HALS=Halliburton BA=Baker Atlas BPB=(now Weatherford)
Formation Imaging Tools –Resistivity Imaging Tools
Higher resolution than acoustic tools (1 cm)
Coverage of the borehole depends on hole size and tool type
Oil-based mud special problem (resistive muds)
Resistivity measurements are not calibrated
SPECIAL TOOLS
Image Logs ═════════════════════════════════════════════════════════════════════════
4_____________________________________________________________________________________________
© PetroSkills, LLC., 2016. All rights reserved.
COPYRIGHT
ELECTRICAL IMAGES: DATA ACQUISITION
Raw data includes electrode readings, caliper and x-, y-, and z-axis accelerometer and magnetometer readings.
Borehole deviation and pad 1 tool orientation are determined form the magnetometers.
Sample rate is very high (120 samples per foot) resulting in large digital file size.
Areal coverage is a function of tool of width and number of pads. In general 40 to 80% of the borehole face is imaged.
Depth of investigation is small (less than an inch). Drilling mud must be conductive!
SPECIAL TOOLS – BOREHOLE IMAGING
Formation Imaging ToolsFormation Microscanner (Schlumberger)
═════════════════════════════════════════════════════════════════════════
Special Petrophysical Tools: NMR and Image Logs Core
© PetroSkills, LLC., 2016. All rights reserved._____________________________________________________________________________________________
5
COPYRIGHT
ACOUSTIC IMAGING TOOLS (TELEVIEWERS)
Tools are centralized in the well and a rotating transducer emits and records sound waves.
Acoustic amplitude and travel time are recorded and processed into images.
Tools must be in center of well so that reflections strike and return at correct reflection angle.
CBIL tool rotates at 6 revs/s and sample rate is 250 samples per rotation.
VR is 0.3in at logging speed of 1200ft/hr; can be run in oil based muds.
SPECIAL TOOLS – BOREHOLE IMAGING
Formation Imaging Tools –Acoustic Imaging Tools
Resolution lower than resistivity tools (3 cm)
360 coverage of the borehole.
Can be run in oil or water-based mud.
Provides a calibrated amplitude and travel time measurement.
Image Logs ═════════════════════════════════════════════════════════════════════════
6_____________________________________________________________________________________________
© PetroSkills, LLC., 2016. All rights reserved.
COPYRIGHT
═════════════════════════════════════════════════════════════════════════
Special Petrophysical Tools: NMR and Image Logs Core
© PetroSkills, LLC., 2016. All rights reserved._____________________________________________________________________________________________
7
COPYRIGHT
Image Logs ═════════════════════════════════════════════════════════════════════════
8_____________________________________________________________________________________________
© PetroSkills, LLC., 2016. All rights reserved.
COPYRIGHT
IMAGING: STATIC AND DYNAMIC NORMALIZATION
Static Normalization Color scale normalized over entire
processed interval.
Identical colors anywhere on imagerepresent same resistivity levels andreflect major changes in lithology / fluid composition.
Dynamic Normalization Colors determined using mean and
variance of a histogram of short(2-3 ft.) interval.
Colors can only be compared over short distances.
Small-scale features enhanced; not picked up on the static images.
Dynamic normalization enhances the contrast of the image, highlightingfine-scale sedimentary features such as cross-bedding or pebbles
IMAGE LOGS
Static vs. Dynamic Image Normalization
STATIC NORMALIZATION
DYNAMICNORMALIZATION
═════════════════════════════════════════════════════════════════════════
Special Petrophysical Tools: NMR and Image Logs Core
© PetroSkills, LLC., 2016. All rights reserved._____________________________________________________________________________________________
9
COPYRIGHT
STATIC VS. DYNAMIC IMAGE NORMALIZATION
STATIC VS. DYNAMIC IMAGE NORMALIZATION
Image Logs ═════════════════════════════════════════════════════════════════════════
10_____________________________________________________________________________________________
© PetroSkills, LLC., 2016. All rights reserved.
COPYRIGHT
LWD IMAGES – RESISTIVITY – DISCRETE FRACTURE
APPLICATIONS: FRACTURE IDENTIFICATION
Open Fracture
An open fracture appears as a low resistivity feature that cuts or crosses through the bedding planes.
The fracture is considered ‘open’ and is filled with the low resistivity drilling mud creating the dark sinusoid on the image.
═════════════════════════════════════════════════════════════════════════
Special Petrophysical Tools: NMR and Image Logs Core
© PetroSkills, LLC., 2016. All rights reserved._____________________________________________________________________________________________
11
COPYRIGHT
TURNING RESISTIVITY CHANGES INTO DIP DATA
12 3
4
567
81 2 3 4 5 6 7 8
APPLICATIONS: FRACTURE IDENTIFICATION
Healed Fractures Fracture filled with highly resistive material - calcite
Image Logs ═════════════════════════════════════════════════════════════════════════
12_____________________________________________________________________________________________
© PetroSkills, LLC., 2016. All rights reserved.
COPYRIGHT
APPLICATIONS: STRUCTURAL INTERPRETATION
Structural Images can identify faults, folds, and
other structural features.
These features enable the geologist to understand the structural environment in great detail.
The example illustrates a fault plane intersecting the wellbore, with vertical displacement of the sediments.
Courtesy of Weatherford
APPLICATIONS: STRATIGRAPHIC INTERPRETATION
Stratigraphy Images can identify cross-
bedding, channels, ripples, and other stratigraphic features.
These features enable the geologist to understand the depositional environment, enabling description of reservoir geometry and production characteristics.
Cross-bedded sandstone
Soft sediment slump/collapse structure
Series of ripple small ripple beds
Courtesy of Weatherford
═════════════════════════════════════════════════════════════════════════
Special Petrophysical Tools: NMR and Image Logs Core
© PetroSkills, LLC., 2016. All rights reserved._____________________________________________________________________________________________
13
COPYRIGHT
APPLICATIONS: POROSITY / LITHOLOGY
Porosity / Lithology Images can help identify
lithology changes, and “see” certain types of secondary porosity, including vugs, casts, and micro-fractures.
Large vugs (individual pores) are clearly visible on the image
APPLICATIONS: THIN BED ANALYSIS
Thin-Bed Images can help identify and
quantify the amount of reservoir rock within thinly laminated sand-shale intervals.
Laminated sand-shale sequence
Image Logs ═════════════════════════════════════════════════════════════════════════
14_____________________________________________________________________________________________
© PetroSkills, LLC., 2016. All rights reserved.
COPYRIGHT
APPLICATIONS: DEPTH AND ORIENTATION OF CORES
Core Depth / Orientation Log section intersects a high
angle strike-slip fault showing the NW-SE strike and evidence of the fault breccia and slip planes.
The photo is of a core splinter taken across the zone and confirms the image interpretation. Horizontal bedding can be seen on the face of the splinter and broken fractured breccia on the outside.
Breccia
Fault plane
BOREHOLE BREAKOUT
Breakout
Courtesy of Weatherford
═════════════════════════════════════════════════════════════════════════
Special Petrophysical Tools: NMR and Image Logs Core
© PetroSkills, LLC., 2016. All rights reserved._____________________________________________________________________________________________
15
COPYRIGHT
CALIBRATION OF BHI TO CORE: KEY STEPS
Ideally, any BHI should be calibrated to core.
Lithology, reservoir properties can be correlated to image attributes.
Sedimentological features visible on the cores identified on corresponding BHIs.
Calibrated image facies scheme extended to uncored intervals and, ultimately, to nearby wells.
Fracture properties (aperture, clay smearing), small scale diagenetic effects can be calibrated directly.
BHI TO CORE REALITIES
Image logs can replace cores to some extent.
Image logs are more continuous, faster and easier to acquire.
Core recovery is not optimal in unconsolidated sands.
Coring often induces hole problems and can jeopardize other well objectives.
Coring is more costly (x10), has greater risks.
Sidewall cores may be useful to confirm BHI analysis where continuous core not available
BUT, a continuous core is required for BHI calibration
AND, BHI does not give Φ, k, “m”, “n”, etc.
Image Logs ═════════════════════════════════════════════════════════════════════════
16_____________________________________________________________________________________________
© PetroSkills, LLC., 2016. All rights reserved.
COPYRIGHT
DEP. ENVIRONMENT ANALYSIS WITH BHI
The knowledge of depositional environment in the subsurface enables better understanding of: Depositional history of a sedimentary basin
Spatial relationships of particular facies (e.g., source rocks, reservoirs and seals)
Geometry of reservoir bodies, essential for static reservoir modeling
Internal heterogeneities of reservoirs, and the associated variations in permeability anisotropy
Variations in reservoir properties (e.g., grain size, porosity, permeability and diagenesis)
BHI ENVIRONMENTAL RECONSTRUCTION
═════════════════════════════════════════════════════════════════════════
Special Petrophysical Tools: NMR and Image Logs Core
© PetroSkills, LLC., 2016. All rights reserved._____________________________________________________________________________________________
17
COPYRIGHT
INTEGRATED CORE – FMI LOG INTERPRETATION, ESTUARY DEPOSITS, MIDDLE EAST
Multiple stacked reservoir sandstones
Problem: Prediction of the size, shape and trend of the individual sand bodies to aid field
development
>700 ft of conventional core is available together with FMI log
Interpretation of FMI is complicated by the presence of multipleoil/water contacts
4700-5867.5 ft(4700-1788 m)
WAVE DOMINATED ESTUARY
Alluvial Valley
DeltaDistributary Channels
Coastal Plain
ShallowMarineShelf
Central Basin
L3L8
L7Bay
Mouth Bar
L5
L6
Delta Front
L4L2
Carb. Buildup
L1
Interpretation based on conventional cores
DIAGRAMMATIC RECONSTRUCTION OF DEPOSITIONAL ENVIRONMENTS
Coastal Plain
Central Basin
Delta Front
Delta Distributary Channels
Alluvial Valley
Carbonate Buildup
Shallow Marine Shelf
═════════════════════════════════════════════════════════════════════════
Special Petrophysical Tools: NMR and Image Logs Core
© PetroSkills, LLC., 2016. All rights reserved._____________________________________________________________________________________________
1
COPYRIGHT
Note discrepancy between CMD and MD. This is common and must be accounted for.
5620‘(1712.9m)
5619‘(1712.7m)
5618 '(1712.4m)
O/W Contact
LITHOFACIES 1: CROSS BEDDED ALLUVIAL VALLEY SANDS
High angle cross bedding in fluvial channel sands. Note FMI color change at O/W Contact (5625.2′; 1714.5m).
LITHOFACIES 1: CROSS BEDDED ALLUVIAL VALLEY SANDS
1713.6m
1713.9m
1714.2m
1714.5m
1714.8m
1715.1m
Image Logs ═════════════════════════════════════════════════════════════════════════
2_____________________________________________________________________________________________
© PetroSkills, LLC., 2016. All rights reserved.
COPYRIGHT
No Core
The base of the channel at 5736.3′ (17.48m) is flat and rests on underlying shales. Overlying fluvial channel sands are cross bedded (moderate to high angle). Occasional intervals of low angle cross bedding occur in the sands (5725.5′; 1745m). The channel top is marked by a thin shale interval (yellow) that represents an episode of fine grained sediment deposition caused by avulsion of the channel complex.
LITHOFACIES 1: ALLUVIAL VALLEY, COMPLETE CHANNEL SEQUENCE
1744.9m
1746.5m
1748.1m
Distributary channel sands are cross bedded and contain scattered rip-up clasts of shale (5553′ – 5554′; 1692.5m – 1692.9m). A scour feature occurs within this channel (5555′ - 5556′; 1693.2m – 1693.5m).
LITHOFACIES 2: DELTA DISTRIBUTARY CHANNEL
1692.2m
1692.5m
1692.8m
1693.2m
1693.5m
1693.8m
═════════════════════════════════════════════════════════════════════════
Special Petrophysical Tools: NMR and Image Logs Core
© PetroSkills, LLC., 2016. All rights reserved._____________________________________________________________________________________________
3
COPYRIGHT
5046’(1438 m)
5175’(1577 m)
LITHOFACIES 2: DISTRIBUTARY CHANNEL
Rooted and burrowed shales of the swamp environment (5568.0′–5577.2′; 1697m–1699.9m) occur above laminated shales and low angle cross bedded sands of the estuary bay environment. The thin sand beds probably originated as distal crevasse splay deposits.
LITHOFACIES 3: POORLY DRAINED SWAMP ON ESTUARY BAY
1697.7m
1698.3m
1698.9m
1699.6m
1700m
1700.8m
Image Logs ═════════════════════════════════════════════════════════════════════════
4_____________________________________________________________________________________________
© PetroSkills, LLC., 2016. All rights reserved.
COPYRIGHT
5578‘(1700.2m)
5579‘(1700.5m)
LITHOFACIES 3: POORLY DRAINED SWAMP ON ESTUARY BAY
This lithofacies is characterized by conformable cross bedding that represents the preservation of low angle bar forms by capping shales. Delta front sands contain scattered shale clasts.
LITHOFACIES 4: DELTA FRONT SANDS AND SHALES
1641.9m
1642.3m
1642.6m
1642.9m
1643.2m
1643.5m
1643.8m
═════════════════════════════════════════════════════════════════════════
Special Petrophysical Tools: NMR and Image Logs Core
© PetroSkills, LLC., 2016. All rights reserved._____________________________________________________________________________________________
5
COPYRIGHT
5390‘(1642.9m)
5391‘(1643m)
LITHOFACIES 4: DELTA FRONT SANDS AND SHALES
Laminated shales with sand-filled burrows. Burrow intensity increases upwards. The shale laminations dip at very low angles (<5 degrees). The basal shales grade downward into delta front deposits (contact at 5372.9′; 1637.7m) and drape over low angle bar forms reflecting the surface morphology of underlying delta front deposits.
LITHOFACIES 5: CENTRAL BASIN SHALES
1636.5m
1636.8m
1637.1m
1637.4m
1637.7m
Image Logs ═════════════════════════════════════════════════════════════════════════
6_____________________________________________________________________________________________
© PetroSkills, LLC., 2016. All rights reserved.
COPYRIGHT
5371‘(1637.1m)
Alluvial Valley
DeltaDistributary Channels
Coastal Plain
ShallowM arineShelf
Central Basin
L3L8
L7Bay
M outh Bar
L5
L6
Delta Front
L4L2
Carb. Buildup
L1
LITHOFACIES 5: CENTRAL BASIN SHALES
Coarsening upwards sequence, consisting of shales that grade upwards into sands. The sands are burrowed. Some low angle cross bedding is preserved.
LITHOFACIES 6: BAY MOUTH BAR SANDS
1575.8m
1576.4m
1577.0m
1577.6m
1578.3m
1578.9m
1579.5m
═════════════════════════════════════════════════════════════════════════
Special Petrophysical Tools: NMR and Image Logs Core
© PetroSkills, LLC., 2016. All rights reserved._____________________________________________________________________________________________
7
COPYRIGHT
Extensively bioturbated, very fine grained sands. Few primary sedimentary structures exist due to burrowing. Burrow types indicate a shallow marine environment of deposition. Individual sands have variable thickness and coarsening upwards sequences are common.
5179‘(1578.6m)
Alluvial Valley
DeltaDistributary Channels
Coastal Plain
ShallowMarineShelf
Central Basin
L3L8
L7Bay
Mouth Bar
L5
L6
Delta Front
L4L2
Carb. Buildup
L1
Shale
Mixed shaleand sand
Dominantlysand withsome shale
Plain Light UV Light
GS/CU
LITHOFACIES 6: BAY MOUTH BAR SANDS
Intensely bioturbated intervals exhibit random FMI patterns.
LITHOFACIES 7: MARINE SHELF, BURROWED SHALES
1669.4m
1669.7m
1700m
1670.3m
1670.6m
Image Logs ═════════════════════════════════════════════════════════════════════════
8_____________________________________________________________________________________________
© PetroSkills, LLC., 2016. All rights reserved.
COPYRIGHT
5479‘(1669m)
5480‘(1670.3)
Alluvial Valley
DeltaDistributary Channels
Coastal Plain
ShallowMarineShelf
Central Basin
L3L8
L7Bay
Mouth Bar
L5
L6
Delta Front
L4L2
Carb. Buildup
L1
LITHOFACIES 7: MARINE SHELF, BURROWED SHALES
Shallow shelf carbonate deposits (4841′ - 4846′) rest on burrowed shales of Lithofacies 7 (shelf mudstones). The carbonates lack obvious evidence of internal sedimentary structures.
No Core
Alluvial Valley
DeltaDistributary Channels
Coastal Plain
ShallowMarineShelf
Central Basin
L3L8
L7Bay
Mouth Bar
L5
L6
Delta Front
L4L2
Carb. Buildup
L1
LITHOFACIES 8: SHALLOW SHELF CARBONATES
1475.8m
1476.5m
1477.1m
1477.7m
═════════════════════════════════════════════════════════════════════════
Special Petrophysical Tools: NMR and Image Logs Core
© PetroSkills, LLC., 2016. All rights reserved._____________________________________________________________________________________________
9
COPYRIGHT
CROSS BEDDED SANDSTONE
1575.8m
1576.4m
1577m
1578.9m
1577.6m
1578.3m
1579.5m
CLASSIC DEPOSITIONAL SETTINGS
http://www.eos.ubc.ca/resources/slidesets/clastic/clastic.html
Image Logs ═════════════════════════════════════════════════════════════════════════
10_____________________________________________________________________________________________
© PetroSkills, LLC., 2016. All rights reserved.
COPYRIGHT
LEARNING OBJECTIVES
identify the types of image logs and technology used
identify the application of image logs for geological and petrophysical data
integrate the image data with core and other log data to reconstruct depositional models
You are now able to:
═════════════════════════════════════════════════════════════════════════
Special Petrophysical Tools: NMR and Image Logs Core
© PetroSkills, LLC., 2016. All rights reserved._____________________________________________________________________________________________
11
COPYRIGHT